Types of Necrosis: unprogrammed cell death

Question 1

What is necrosis?

Answer 1

Accidental, unprogrammed cell death in response to irreversible cell injury

Question 2

What cellular components are damaged and so trigger necrosis?

Answer 2

Membranes

Question 3

What 2 responses are triggered by damage to cell membranes in necrosis?

Answer 3

Lysosomal digestion, cell leakage triggers inflammatory response

Question 4

Are there different types of causes for necrosis?

Answer 4

Cause is always pathological

Question 5

Give 4 examples of pathological causes that trigger necrosis?

Answer 5

Ischaemia, toxins, trauma, infections

Question 6

How do calcium ions cause mitochondrial damage which leads to necrosis?

Answer 6

Calcium ions enter cell which stimulates Mitochondrial Permeability Transition Pores (MPTP) to open in inner membrane, so ATP is depleted

Question 7

How does calcium cause DNA damage which leads to necrosis?

Answer 7

Calcium activates enzymes that cause DNA damage, as well as nuclear and membrane damage

Question 8

How does free radical damage occur, that leads to necrosis?

Answer 8

Free radicals are highly reactive unpaired electrons that modify adjacent molecules eg. proteins, nucleic acids, lipids

Question 9

How do free radicals affect interacting molecules in auto-catalytic reactions?

Answer 9

Converts interacting molecules into free radicals

Question 10

What are the 2 ways in which antioxidants protect against free radical damage, preventing necrosis?

Answer 10

Block free radical formation, inactivate free radicals

Question 11

What 3 vitamins are antioxidants that protect against free radical damage, preventing necrosis?

Answer 11

Vitamins A,C,E

Question 12

What substance is an antioxidant that protects against free radical damage, preventing necrosis?

Answer 12

Glutathione

Question 13

Which 2 immune cells produce ROS free radicals in large amounts?

Answer 13

Neutrophils, macrophages

Question 14

What is coagulative necrosis caused by?

Answer 14

Ischaemia

Question 15

What are the 2 microscopic features of coagulative necrosis?

Answer 15

Cells have lost their nuclei, eosinophilia (hyper-pink H&E stained cytoplasm)

Question 16

What is the macroscopic feature of coagulative necrosis?

Answer 16

Necrotic area is paler than healthy tissues

Question 17

What causes coagulative necrosis in the kidney, and what does this lead to?

Answer 17

Thromboembolism, which causes coagulative necrosis leading to renal infarct

Question 18

What is a thromboembolism?

Answer 18

Thrombus breaks off and travels through bloodstream, blocking off vessel in which it gets stuck

Question 19

What 2 conditions cause liquefactive necrosis?

Answer 19

Bacterial infection, stroke

Question 20

What is the macroscopic feature of liquefactive necrosis?

Answer 20

Viscous liquid mass formed as dead tissue is digested

Question 21

What causes ischaemial stroke that leads to liquefactive necrosis in brain?

Answer 21

Thromboembolus blocking cerebral artery

Question 22

How does ischaemial stroke affect brain’s structural strength?

Answer 22

Surface collapses

Question 23

What causes gangrenous necrosis?

Answer 23

Severe ischaemia

Question 24

What causes dry gangrene?

Answer 24

Lack of blood supply to tissues, so it is a form of coagulative necrosis that occurs in different tissue planes

Question 25

What causes wet gangrene?

Answer 25

Dry gangrene exposed to bacterial infection, also a form of liquefactive necrosis

Question 26

Where in the body does gangrenous necrosis generally occur?

Answer 26

Extremities

Question 27

What are the 2 macroscopic features of gangrenous necrosis?

Answer 27

Blackened skin, putrefaction (rotting)

Question 28

What are the 2 microscopic features of liquefactive necrosis?

Answer 28

Macrophages, neutrophils

Question 29

How are the microscopic features of wet and dry gangrene different?

Answer 29

Wet is similar to liquefactive necrosis features, dry is similar to coagulative necrosis features

Question 30

What causes caseous necrosis?

Answer 30

Foreign noxious stimulus eg. tuberculosis can't be destroyed by immune system, so is contained

Question 31

What stain is used to confirm a diagnosis of tuberculosis, and what colour does it stain the bacteria?

Answer 31

Ziehl-Neelsen stain, can see red acid-fast bacilli

Question 32

What is the most common cause of caseous necrosis?

Answer 32

Tuberculosis, usually in lungs

Question 33

What structure is formed by caseous necrosis?

Answer 33

Caseating granuloma that contains necrotic tissue and a border of fibroblasts and macrophages

Question 34

What is the macroscopic feature of caseous necrosis?

Answer 34

Cheese-like yellow sphere with border

Question 35

What are the 2 microscopic features of caseous necrosis?

Answer 35

Large multinucleated cells, macrophages

Question 36

What condition causes fat necrosis?

Answer 36

Acute pancreatitis

Question 37

What enzymes are released from the inflamed pancreas in acute pancreatitis, that causes fat necrosis?

Answer 37

Pancreatic lipase

Question 38

What is the macroscopic feature of fat necrosis?

Answer 38

Swollen hemorrhagic pancreas

Question 39

What are the 3 microscopic features of fat necrosis?

Answer 39

Infiltrate of macrophages, anucleated adipocytes, unclear borders between adipocytes